Centrifugal filtration



Nov. 3, 1953 A. H. SCHUTTE CENTRIFUGAL FILTRATION 2 Sheets-Sheet 1 Filed Sept. 1, 1949 A TTO Nov. 3, 1953 A. H. SCHUTTE 2,657,803

CENTRIFUGAL FILTRATION Filed Sept. 1, 1949 2 Sheets-Sheet 2 INVENTOR.

16 17 xi/ 591491173127 J'ckaie BY WM ATTEY Patented Nov. 3, 1953 UNITED ESTATES i PATFEN-T [CE CENTRIFUGAU'FIETRNIION r rAugustiHnSchutte; Hastings on Hudson, N. Y., i iassignor to .TheiLummus Gompany, eNewXork, .N. Y., awcorporation of Delaware -"-"Aiiplicatioh septmber 1,"1949, serial-No? 113,605

-' charge; An exampleofisuch a charge is-a chilled dewaxing' mixture containing a so1vent-such:=as

=methyl-"'ethyl keton'e benzol. =Heretofore; in the centrifugal 'filtration' of'such a charge serious difiiculties have beerr encounteredmajor difficulty has been thatuponccontinuousdeed-' ing of' the charge to the-.icentrifugethe' heavy s'olid component would build up at a-repose'angle which permitted the' charge slurry to discharge in a thin fi1mand athigh-velocity through the solids outlet of the centrifuge, with quite insufiicient filtration time. Difliculties were also encountered in =the-'-'r'emo'val of the accumulated solidsfrom the centrifuge. Gentiifu'gal sepa- --rators have been employed "whichoperato on a "cyclic basisand remove the accumulated sol-idsby mechanically actuatedknives'orplows: However; many materials: become agglomerated or glazed over by the action of the-knivesorplows andbecome impervious to" further liquid fiow. *Wax'cake is one'of such materials.

' Important objects of the present invention-are "to eliminate the sziiddifli'culties to'prov-idefor ""such'elimination in a-simpleand satisfactory manner; to""provide-"for satisfactory removal: of

the accumulated solids ;by."'hydrostatict means with consequent improvement of filter performance; to provide, in. such removakfor' the "employment" of a liquid" independentfof' the'charge and for'the' exclusion ofsuch'li'quid from the;fil-' tration region of 'the centrifuge';'"and to provide.

' satisfactory "apparatus of "simple construction for attaining the desired advantages.

' 'Otherlobjects and advantagesof the invention Willappear. from the following descriptiomtaken in connection with theaccompanying"drawingsi;

' Inthe drawings:

'Fig. 1 is a view, partly in sectioniandpa'rtly in elevation; showing one formof the improved centrifugal filter apparatus;

Fig. 2 is. an enlargedsectional viewof a lower. 45

portion of the centrifuge;

Fig. 3 is a View similar toFig. 1,=-sh0wing a modified. form of the apparatus;

Fig. 4 is a-cletailsection on *theline 4 4 of Fig. 3'; and 1 Fig. 5 is a sectional viewof aside portion of the centrifuge rotorg ishowing another -modification.

' The apparatus, inthe form shown-in 'Fig. 1;: ineludes axdrumelikexhousingzihavmg aa circumtere e entialsidezwall ll abottom wall Icand amemovable topiclosure 3.9-. Abearing 54 for -a drivevshaft 5 is mountedvcentrallympon:the bot-tomuwa-lh of theh'ousing;.:ami:the centrifuge-rotorfi issecured, through a hub portion 13' thereof, toixtherdrive shaft.

As showmttheorotor Eff-has .aiicylindricalfizimwe perforate circumferential side zwall 8 (and :a bottom'uwall Scbearingvtheehub 1. :zThe SidBzWflJl 8 bears at-iits upper: enclrianzannulargzlipi I II which w extends inwardly towardatheraxis ofzthemotorand "a? is ofcuniformcradial width.:;i.:Ina.therpresentiintanceysaid alip isaitormedofzispacedtuppemand flower csheetelikeportions :2 Illa; andml flbirrespectively,'.and a'lconnectingrportionii 0c whichizfonns ":thecmneicedge. of:the1lip;::s'I-herupper portion .4 0a xtends 1 radiallysoutwardvbeyond t'hel side wall 8 and has ar=downturried1annu1ar flanged 0dr spaced inwardly fromzth'e housing wall I; {Beneath-the zo-axlipaportionc I flbnranrannular member I I isecu-red thereto formsg'iwithzsaida' lip rpo'rtionsand. itheaiside wall 8: of the; rotor; an annularefiltrate: outlet f-zichannelrll .A 'rcircular. series?ofports'-'I3 int-the imrotor wall :8iafiordroutlet-forrthe filtrate.:iEilter 25zpipesa I4, in a;:cireular series-arounditheraxis. of

-'.-':lthe: rotomdepend. rfromrthe-lmemberi I Is? In..:the rrdrawingrthe c'pipesin .thev back-.-r area-omittedi to simplify :thedl'lustration. Y, Each apipe is rdetachblysconnected toithermember I l eas at I ixand is cperfor-atedi alongi itsa: length sand around-,eits m circumference: The-pipeis covered with woven crwire cloth which is. overlaid with -8;I.Sl1itflb16;;fi1t6l :nmedium such:asclothpfilteriduck, or the like. At zztheir uppernend tthe pipes Iopen' intoithe. filtrate gochannel ILandrtheyareiclosed atrtheir :lower end andcspaced above the. :bottomww'all. 1'." The pipes are r arranged son: close circumferential; spacing 1179111112. at a sufficientvdistance iromn't-hensolid'awall 82 olrsthe lrotonito permit :accumulation: of -heavy 6280318. orrdirt without plugging the fllterg'cloth.

"zlTheobottom' wall Siofit-he rotor has aroiroular series of holes I6=close'to:the;wall 8=ofithe rotor :and nbeneath:saidwwall there is an annular channel Hformed byithe wiall, fl asportion.of.-the-side wall 8 which extends below the wall Brand an 1 'inwardlyraextending-z'annular 'fiange 5', I 8. 9-. Said ifflallgef-hais a icirculariseries or; bleed holes-5H at .r a radial: distance: from i the rotor *axis: intermeta-zdiate' the. radial distance of the holes' t6 1 and the =radial distance of the inner: edge: of. the cfiange 1 I8.:1 A: narrow-flared skirt. flange zflaextendsfrom the lower end of the rotor wall 8 andvhasrtits lowerten'd adjacent a iow;:annularzwal1*2 I=zextend- '2;ingcupwardly fromithesbottom wall tofitherhousning: rAnannular schannelwZIu-for: receiving-solid material discharged from the rotor surrounds the upper portion of the rotor. This channel is defined by the side wall I of the housing together with an annular member 23 having an outwardly extending lower portion secured to said wall and an inwardly extending upper portion located inwardly of the outer depending flange llld of the rotor lip ID. The housing wall I has a nozzle 24 for draining the channel 22, and also a nozzle 25 for draining the bottom space within the housing, between the wall I and the upstanding wall 2|. A nozzle 26 is borne by the bottom of the housing for draining the bottom space surrounded by the wall 2|.

A charge delivery pipe 21 extends downwardly through the open end of the rotor to a point near the bottom 9 thereof. The charge delivered to the bottom is constrained to flow outwardly therealong by a fiat annular baffle 28 borne by the bottom 9 at a level slightly above the lower end of the pipe 21. An upstanding annular bafile 29 is also borne by the bottom of the rotor. This baflle is located directly outside of the filter tubes I4 and extends above the lower end of the tubes. It serves to receive against it the charge passed beneath the baffle 28, and deflect the charge upwardly.

At a lower level than the bottom 2 of the housing there is a reservoir or surge tank 30 for a liquid independent of the charge to be separated and heavier than any component of the charge. A pipe line 3| leads from the bottom drain nozzle 26 of the housing to the upper portion of the tank 30. A pipe line 32 connects the bottom of the tank with the inlet of a pump 33 and, from the pump outlet, a pipe line 34 leads upwardly to the space surrounded by the annular channel I! at the bottom of the rotor. At the upper end thereof, the line 34 has a discharge end 35 outside of the channel I! and directed into the open side of the channel to discharge into the channel a jet of the liquid. The pipe line 34 has a valve 36 which may, as indicated, he of an air-operated type. A timer device 31 controls the operation of said valve. Air is admitted to the timer at 38 and is admitted by the timer to the valve through a line 39. The timer may be of a standard type suitable to admit the air to the valve for opening same at suitable intervals. The charge delivery pipe 21 also has an air-operated valve 40 under control of the timer. The timer is adapted to admit air through a line 4| to effect clo- Sure of the valve 4!] when the valve 36 is opened.

Provision is made for recirculation and cooling of the independent liquid when the separating operation is refrigerated. A pipe line 42 leads from the line 34 at a point between the pump 33 and the valve 36. Through a valve 43, the line 42 is connected to a pi e line 44 leading to the drain line 3|. A cooler or refrigerating device 45 is connected into the line 44. Valve 43 is loaded to open under a predetermined pressure in the line 42 when the valve 36 is closed.

A deliverv pi e 46 for wash liouid extends into the rotor through the open end of the latter. This pipe exte ds throughout most of the depth of the rotor and has a series of discharge ports directed outwardly to discharge jets of wash liquid against the separated solids within the rotor.

The a paratus just described is operated as follows: It will be assumed, for example, that the charge to be separated is a chilled dewaxing mixture of wax, oil and a solvent lighter than wax, such as methyl ethyl ketone-benzol. With the valve 36 of the independent liquid line 34 closed, the rotor is operated with a stratum S of the independent heavy liquid at the wall 8 of the rotor. A minimum radial depth of this stratum is maintained owing to the radial location of the bleed holes I!) of the channel so that the stratum is substantially spaced outwardly from the filter tubes l4. Said minimum depth is sufilcient to enable the liquid of the stratum to seal the holes I 6. The charge delivered through the pipe 21 passes beneath the bafile 28 to the baffle 29 and is directed upwardly thereby along the filter tubes. The liquid component of the charge passed through the filter medium of the tubes fiows into the channel l2 at the upper end of the tubes and is discharged through the ports l3. The discharged filtrate is collected within the bottom space of the housing, between the wall I and the wall 2! and is discharged through the nozzle 25.

Separated solid material of the charge accumulates and gradually builds up from the stratum S to an inner level indicated by line L in Fig. 1 and forms a cake. During the filtration cycle the cake is washed by liquid discharged from the pipe 46. Before the separated solid reaches the inner edge of lip ID the filtration cycle is concluded by operation of the timer 31 to close the valve 40 and open the valve 36 and permit delivery of the heavy independent liquid through the line 34 to the channel I! at the bottom of the rotor. The rate of such delivery exceed the discharge capacity of the bleed holes I9 of the channel so that the heavy liquid flows through the holes I6 into the rotor and augments the stratum of heavy liquid to increase the radial depth thereof to a substantial extent but insufficient to bring the stratum into contact with the filter medium. Thereby, escape of heavy liquid through the filter pipes is prevented. The increase in the radial depth of the stratum is limited by the radial position of the inner edge of the flange [8. Any additional liquid delivered to the channel after said edge has been reached is discharged past the edge and collected, along with the liquid discharged through the bleed holes [9, within the bottom space of the housing, surrounded by the wall 2|. Thence, the liquid drains through the nozzle 26 and the line 3| to the tank 36.

Increase in the radial depth of the stratum of heavy liquid within the rotor, in the manner just described, causes displacement of the separated solid radially inward and advances the relatively dry cake thereof past the inner edge of the lip ID at the top of the rotor. The inner portion of the cake is then discharged past the lip and radially outward to the wall I of the housing along which it falls into the collecting channel 22 from which it is withdrawn through the nozzle 24. After a time sufficient for discharge of an adequately drained portion of the cake, the timer 31 operates to close the valve 36 and stop delivery of the heavy liquid through the line 34. Bleeding of the liquid through the holes IQ of the channel I! then reduces the radial depth of the stratum of heavy liquid within the rotor to the minimum depth determined by the radial position of the bleed holes. Reduction of the depth of the stratum permits recession of the charge within the rotor radially outward to a position spaced from the inner edge of the lip. The timer also causes opening of the valve 40 the pipe line 69.

as-canoe and resumption of charge delivery--through-pipe 21, and the filtration cycle is repeated. Fig. 3"-ShOWS anapparatuesi-milar to the one shown in-Figsd and-2 except for-modification of the mechanism:for-increasing and decreasing the radial depth of thestratum of heavy liquid within therotor. In this modification the'bleed holes are omitted from the-iiang'e,-' here designated I 8a,

For supplying' the heavy liquid there is a tank 4t substantially elevated above the level of the channel It. A pipe line 49 leads fronr said tank to the scoop 37. The scoop-has a-vertical portion with a swivel mounting i! on-the bottomwall 2 of the-housing and a-swivel'- connection 5i with For turning the scoop on its axis there is a reciprocating fluid motor"52- or other suitable device controlled by a timer-31a.

The motor may; as indicated, be operated byair A plungertzi of-the motor is-operaa crank armfilfiXed to the vertical'portion of the scoop." As shown; the timer isalso opera-" tively connected to the :charge delivery valvedfi through the air pipeline M, as in the" form'or" the apparatus previously described.

In the operation of. the apparatusshown in Fig.

3 the scoop i-l' is adjusted radially depthwise' oi the channel i; to a positionior: maintaining within the channel the deptn'of liquid required to determine the minimum radial depth" of the stratum of heavy liquidwithin the rotor. .Con-

. tact of the rapidly rotating body'of liquid in the channel with the scoop. then obstructs flow: of

. liquid from the scoop into the channeLFThefiltration cycle will be concluded. by operation ofithe timer tic to effect; through the motor 52,.withdrawal of the scoop from the channel; ".iThen, the liquid will flow through the linei iii and be V. discharged by the scoop into the channel to in- .creasethe radial depthjof the stratum S within the. rotor to a levelshort ofthe filter pipesl l,

-ior efiecting discharge, of the solid materialyas previously described herein; The extent'of said withdrawal otthe scoop determines theincrease in. depth. of the stratum through, control; ofthe depth of. the ,liuuidwithin the channel" i'i i' This .depth, as determined by the withdrawn position of thescoop, is. lessthanthe totaldepth of, the

channel so that before-.the.liquid,.reachesl the inner edge oiithe flange. E80: contact ofithe rapidly rotating body. of liquid within theschannelwith ,the scoop again obstructs further edeliveryiof liquid from the tank is.

Attheconclusion of a suitable period for discharge of the solid: materiaLthetimer 37a. operates tocausemovement. of. thescoop 4-1. deeper into the channel ii to. the first-mentioned. posi tion.

the channel and the liquid flowing into. the chan- As the scoop isrso moved,theliquidwithin nelfrom the stratum S isv forced by its; rapid rotation, through the scoop and the pipelifi back to the tank, idagainst the resistance of. thaheacl afforded .by the elevatedhposition of. theitank.

Thereby, the depth of thestratum S is reduced to the desirediminimumh AdjustableHstops. 58 are provided to limit the movement of the scoop in both directions and determine accurately thei 6 r requ-ired maximum and minimum levels on the liquid. inthe-iorm of the inventioirfirstdev scribed; the timer: controls the charge: valve' 49 "to discontinue delivery of-thienharge-tdthe rotor 5 11 during increase of tha -stratum S for dissharge sf of the solidmaterial and tocause resun'iption of --delivery whenthe depth o'f-the stratum is reduced. -In =the-mddificatiori= shown 5y provision a is made for segregation of the indepe'ndentliquid w iron'rth charge withinthe rotor. For that purpose;- the rotor is provided with a'cylindrical membrane 59-- of material= impermeable to "s'aidliqilid i and: to -the" charge The membrane is-'-'looated radially outside' of the filter tubes-andits upper 15 and lower edges are secured by-annulanclips fifi, in -sealed connection to 1 the member I l at the nder 'side of the-lip- It and! to' the-bottom '9 of -the-*-rotor;-=respectively. The mater ial or" i the c i membrane isfiexible. It -'may=a1sobe-stretchable andresilient; or elsethe membrane may be sunt- By" provision of the 'membraneigreater choice of independent liquids is afforded-and the neces- "sity for exact determination of'the liqui'd-levels within the rotor is avoided; In. thefnrmso'f the invention shown in: Figs. '1 and 3 it is. necessary v to employ an independent liquidheavier than any componentof thecharge. For example, in

. wax-oil separation with a solvent such as niethyl ethyl ketoneeben'zol, water or brine may be employed. as the. independent liquid; In the form 4 of apparatus .shown in Fig. 5 a-,,liquid either heavieror lighter than the .cha1'ge.,components may be employed andthe necessity formaintaining the-iliquidat a level clear of thefilter tubes is avoided since the. membrane .williexcludeithe independent. liquid from the. filter .tubes even if .the depth of the. liquid withinthe rotor. should ...exceed the radial depth of the. space between the wall 8 ,andthe filter tubes. For theipurpose, of employing a lighter liquidthe flange formingthe GO-under side of .the channeland here designated 7, I81) may, as shown, be of substantially increased radial width. That enablesthe building up of a suflicient radial head of a lighter liquid within the channel fora required increase of:the.radial depth of the liquid around the outer side of themembrane to-effectcake discharge. The membrane is under balanced pressure at all'times and is-:not

subjected to erosion so that it-should remain Y serviceable for a long time.

The modification shown in Fig. 5 maybe-employed in either the apparatus'shownin Fig. 1 or'that shown in Fig. 3.

Inall 'forms of the apparatus -theztank for. the independent liquid and the timermayserve for control of a battery of separators.

The apparatus is particularly suited for large .---scale: performanceremployingjrfors example, a rotor; 84 inches in diameter and 6.0- inchesgiir depth wand wherein the tubes": 14 afford approximately 200 sq. ft. of filter-:surface,.and acdisplacement of approximately z inches bythe independent .1 liquid for cake-discharge isprovidedzior. The .-.cake discharge step, may be-timed to occur every N nine or. ten minutes, for example. The invention provides in a simple manner for more complete separation and avoids the difficulties previously mentioned herein as incurred in the centrifugal filtration of a mixture containing a solid component heavier than the liquid component, such as the charge mentioned herein. Very simple and reliable apparatus is also provided by the invention for obtaining the desired advantages. While wax-oil separation is mentioned herein as an example of a particularly satisfactory employment of the invention its 1 utility is by no means limited to such separation. It has general industrial utility in the solids-liquid separation field as, for examples, in the separation of chemical salts from slurries and in sugar refining.

While very satisfactory forms of the invention are disclosed, modification of details is possible within the scope of the invention. The present disclosure is merely illustrative and in nowise limiting and the invention comprehends such modifications as will fall within the scope of the following claims.

I claim:

1. A centrifugal filter apparatus for separating a charge mixture including a liquid and a heavier solid, comprising a centrifuge rotor having an imperforate circumferential wall, and a wall at one end thereof to prevent discharge at said end, the rotor being open at its opposite end and there having an annular lip extending from said circumferential wall inwardly toward the axis of the rotor, a plurality of filter conduits within the rotor extending along and spaced around the rotor axis and located intermediate the radial width of said lip each having a longitudinal filter wall, means for progressively delivering the charge to the region of said filter conduits, channel means for discharge of filtrate from said conduits to the exterior of the rotor, an annular channel borne by the rotor at one end thereof with its center on the rotor axis, said annular channel being open at its side toward the rotor axis, means defiining a liquid admission and discharge port connecting said annular channel with a region of the interior of the rotor located at said imperforate wall and spaced radially outward from said filter conduits, said port being independent of said filtrate discharge channel means and the annular channel extending nearer to the rotor axis than said port and said region, a conduit to supply to said annular channel through said open side thereof a liquid independent of the charge from outside of the rotor during rotation of the rotor, for flow through said passage to build up an annular stratum for displacement of separated solid material radially inward for discharge past the inner edge of said lip, means to limit approach of said stratum toward said filter walls to prevent escape of the independent liquid therethrough, and means to effect limited discharge of the independent liquid from said stratum, through said connected port and channel during rotation of the rotor, the said port and the annular channel being correlated with said internal region of the rotor to retain a predetermined minimum radial thickness of said stratum during rotation of the rotor.

2. The centrifugal apparatus of claim 1 wherein the said channel means for discharge of the filtrate and the said annular channel are located at opposite ends of the rotor.

3. The apparatus of claim 1 including means to control delivery of the independent liquid to the annular channel by said supply conduit including a timer operative to periodically interrupt said delivery, for reduction of the radial depth of said stratum.

4. The apparatus of claim 1 including a valve in said conduit for supplying said independent liquid to the annular channel, and mechanism including a timer for periodically opening and closing said valve, for increasing or decreasing the radial depth of said stratum.

5. The centrifugal apparatus of claim 1 wherein the means to limit approach of said stratum to the filter walls comprises an annular flexible membrane impermeable to the liquid of the stratum, borne by the rotor and disposed radially inward of said admission and discharge port, to exclude the liquid from the charge and from the filter walls.

6. The centrifugal filter apparatus of claim 1 including a reservoir for said independent liquid in delivery connection with said supply conduit for the annular channel, and means for effecting return of said liquid, through the said channel, to the reservoir, to alternately increase and reduce the radial depth of said stratum.

7. The centrifugal filter apparatus of claim 1 wherein said means for effecting limited discharge of the independent liquid comprises a bleed port in a side wall of the annular channel and located nearer to the rotor axis than said liquid admission and discharge port.

8. The centrifugal apparatus of claim 1 wherein said supply conduit for the annular channel has a scoop end adjustable to dip into the channel through the open side thereof during rotation of the rotor to remove liquid from the channel and determine the minimum radial depth of said stratum and adjustable reversely for discharge of the liquid into the channel to increase the radial depth of the liquid within the channel.

9. The centrifugal filter apparatus of claim 1 wherein said channel means for discharge of filtrate is located at said lip, the said annular channel is located at the opposite end of the end of the rotor, the said filter conduits are in the form of tubular units borne at one end by said lip and in delivery connection through said end with said channel means for discharge of the filtrate, said units being free at the opposite end thereof, and the apparatus includes releasable couplings between said tubular units and said lip providing for detachment of said units individually.

10. The centrifugal apparatus of claim 1 wherein the open inner side of said annular channel is radially farther from the rotor axis than said filter walls to limit the maximum radial depth of said stratum and a side wall of said channel has a bleed port at a radial position between that of said liquid admission and discharge port and the open side of the channel to determine the minimum depth of said stratum.

11. The centrifugal apparatus of claim 10 including a reservoir for said independent liquid in delivery connection to said supply conduit for the annular channel and elevated above the said channel to provide a head, and means to conduct the liquid discharged from the open side of the channel and from said bleed port to said reservoir.

12. The method of separating components of a charge of a mixture including a liquid and a heavier solid, comprising progressively delivering said charge along a course to a centrifuging zone, continuously centrifuging the charge and a liquid independent of the charge and heavier than any component of the charge and, during the centrifuging, maintaining an annular stratum of said heavy liquid around the outer side of the charge, filtering the liquid component from the charge within a region of said zone spaced radially inward from said stratum of heavy liquid, directing the charge delivery to said filtration region, discharging the filtrate from the centrifuging zone, accumulating the separated solid material in the zone to a radial depth extending inward from said filtration region, halting said charge delivery, delivering additional heavy liquid directly to said stratum along a course independent of the said charge course and clear of said filtration region and of the charge and the separated components of the charge, restraining discharge of the additional liquid from the stratum and establishing a liquid head on the added liquid to augment the radial depth of the stratum to a point closer to but still spaced radially outward from said filtering region and thereby displacing the accumulated separated solid material radially inward, and discharging from the centrifuging step the inner portion of the solid material so displaced.

13. The method of separating components of charge of a mixture including a liquid and a heavier solid, comprising progressively delivering said charge along a course to a centrifuging zone, continuously centrifuging the charge and a liquid independent of the charge and, during the centrifuging maintaining an annular stratum of said independent liquid around the outer side of the charge, filtering the liquid component from the charge within a region of said zone spaced radially inwardly from said stratum of independent liquid, directing the charge delivery to said filtration region, discharging the filtrate from the centrifuging zone, accumulating the separated solid material in the zone to a radial depth extending inward from said filtration region, halting said charge delivery, delivering additional independent liquid directly to said stratum along a course independent of the said charge course and clear of said filtration region and of the charge and the separated components of the charge, restraining discharge of the added liquid from said stratum and establishing a liquid head on the added liquid to augment the radial depth of the stratum and thereby displacing the accumulated separated solid material radially inward, preventing discharge of the independent liquid at the filtering region, and discharging from the centrifuging zone the inner portion of the solid material so displaced.

14. The method of claim 13 including periodically halting said charge delivery and effecting said displacement of the separated solid component as defined in said claim, and, after each discharge of the inner portion of the separated solid material, reducing the radial depth of the said stratum of independent liquid by discharge of the liquid therefrom, and resuming said delivery of the charge to the centrifuging zone.

15. The method of claim 13 including maintaining said stratum of independent liquid segregated from the charge and its components at all times.

AUGUST H. SCHUTTE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,492,168 Hapgood Apr. 29, 1924 1,749,057 Armentrout Mar. 4, 1930 2,165,807 Murphree et al July 11, 1939 2,370,999 Schutte Mar. 6, 1945 2,394,016 Schutte et a1 Feb. 5, 1946 2,398,967 Schutte Apr. 23, 1946 2,431,142 Schutte Nov. 18, 1947 2,440,487 Rayburn Apr. 27, 1948 

